This invention relates to a vehicle and particularly to a suspension and steering system for an agricultural type vehicle by which the ground wheels of the vehicle can be attached through an axle to the frame structure for supporting the frame structure in movement across the ground.
In recent years attention has been given to development of high clearance agricultural vehicles for movement across the ground for transporting materials to be applied to the ground either in granular or liquid form. Developments in the types of materials to be applied have required that the vehicles be capable of movement over bare ground prior to seeding and also over the ground when the crop has emerged and yet further when the crop is well developed. These requirements have led to the development of vehicles specially arranged for these purposes which generally include relatively large ground wheels and raised axles so that the axle can pass over the top of the crop when partly or fully grown. In order to enable the vehicle to move across the ground at relatively high speed, suspension systems are necessary between the ground wheels and the axle to allow suspension movement of the ground wheels to accommodate changes in ground level. In addition it is necessary for the spacing between the ground wheels to be adjustable to allow the ground wheels to pass between the rows of a row crop and to accommodate different spacing of the row crop. These requirements have required special developments in the suspension systems and various techniques have been developed to overcome these problems associated with providing these requirements.
One example of a suspension system for a vehicle of this type is shown in U.S. Pat. No. 5,039,129 of the present inventor. This product is used on a sprayer manufactured and sold widely by Willmar Manufacturing Inc.
John Deere in their U.S. Pat. No. 5,597,172 issued Jan. 28th 1997 disclose a suspension system which they have released commercially on a sprayer. This system uses for each of the four wheels of the vehicle a suspension including a sliding cylindrical strut mounted in a sleeve connected to the axle. A gas bag spring is mounted at the top of the strut. Control of the angular orientation of the strut in the sleeve for steering and attitude control is effected by a scissors linkage connected between the strut and the sleeve. This arrangement is disadvantageous because:
a) It requires sliding movement between the sleeve and the strut which is guided by bushings. In the agricultural situation which requires a high level of movement and requires this to be done in the presence of dust and other contamination, the bushings will receive a high level of wear.
b) The scissors linkage is complex and expensive.
c) The positioning of the gas bag spring at the top of the strut places it high on the machine with the consequent interference with proper view of the ground.
In U.S. Pat. No. 5,353,988 (Gallenberg) issued Oct. 11th 1994 is shown a further suspension arrangement for a sprayer using cross axle beams pivotally connected to the frame with gas bag springs connecting the beams to the frame.
Other examples of suspensions for various types of vehicle using gas bag springs and sliding struts are shown in U.S. Pat. No. 5,364,113 (Goertzen) issued Nov. 15th 1994; U.S. Pat. No. 3,829,118 (Gouirand) issued Aug. 13th 1974, U.S. Pat. No. 3,804,189 (Smith) issued Apr. 16th 1974 and U.S. Pat. No. 3,042,422 (Garnett) issued Jul. 3rd 1962.
It is one object of the present invention to provide an improved suspension system for an agricultural vehicle.
According to one aspect of the invention there is provided an agricultural vehicle for moving over agricultural terrain comprising:
a vehicle frame structure for supporting elements to be transported;
a pair of ground wheels each having a wheel hub mounted on a respective side of the frame structure for rotation of the ground wheel about the wheel hub for transporting the frame structure across the ground in a direction of travel;
two suspension assemblies each for supporting a respective side of the frame structure on a respective one of the wheel hubs for suspension movement of the frame structure in a suspension direction generally upwardly and downwardly relative to the respective hub in response to changes in ground level;
each suspension assembly comprising:
a first member carried on the respective side of the frame structure;
a second member rigidly attached to the respective hub;
a pair of pivotal links interconnecting the first and second members to allow up and down suspension movement of the second member relative to the first member;
and a spring connected between the first and second member so as to generate a spring bias in a direction along the suspension direction to support the respective side of the frame structure on the respective hub.
Preferably the spring is a gas bag.
Preferably the pivotal links generate sideways movement of the first member relative to the second member and wherein the gas bag is arranged to accommodate the sideways movement by sideways flexing of the bag.
Preferably each of the first and second members carries a substantially horizontal platform with the gas bag spring located between the platforms.
Preferably the links are pivotal from a raised position of the wheel in which the links are inclined outwardly of the first member and upwardly, through a horizontal orientation, to a lowered position of the wheel in which the links are inclined outwardly and downwardly.
Preferably the links are substantially parallel.
Preferably the links are substantially of he same length and arranged such that pivot axes thereof on the first member lie in a common vertical first plane and such that pivot axes thereof on the second member lie in a common vertical second plane parallel to the first plane.
Preferably each of the links is pivotally mounted on each of the first and second members by a mounting assembly and wherein each mounting assembly comprises a horizontal mounting pin at right angles to the link, two parallel mounting walls of the respective one of the first and second members with the mounting walls at right angles to the pin, and a collar on the link carried on the pin, the collar being confined against forward and rearward movement in the direction of travel by the mounting walls.
Preferably the mounting walls are coplanar.
Preferably the mounting walls are defined by front and rear walls of a first channel portion of the first member and front and rear walls of a second channel portion of the second member.
Preferably each link consists of the respective collars and a rod there between.
Preferably the first and second members and the links are arranged such that the suspension movement causes inward and outward movement of the wheel relative to the ground and wherein shock absorption for the suspension movement is generated by said movement of the wheel relative to the ground.
Preferably the first member is mounted on an outer end of an axle forming part of the frame structure.
Preferably the axle is extendible to increase and decrease the spacing between the wheels.
Preferably one platform is mounted on top of the second member and wherein the second platform is mounted on the bottom of an arch portion extending from the first member over the top of the second member.
Preferably the wheel is mounted for steering movement about a substantially vertical axis relative to the second member on a steering hub carried on the second member below the links.
Preferably steering movement is effected by a hydraulic cylinder connected between an arm attached to the second member and an arm attached to the wheel hub.
Preferably each of the platforms projects to one side of the first and second members such that the platform on the first member is located above the other to receive the gas bag therebetween.
Preferably the frame structure includes a front frame portion and a rear frame portion, each of the frame portions being substantially rigid and the frame portions being connected so as to be maintained aligned in the direction of travel and so as to prevent steering pivotal movement between the frame portions about a vertical axis;
a front axle mounted on the front frame portion and extending across the frame structure;
a rear axle mounted on the rear frame portion and extending across the frame structure rearwardly of the front axle;
each of the front and rear axles having a pair of ground wheels thereon, each ground wheel having a wheel hub mounted at a respective end of the axle on a respective side of the frame structure for rotation of a wheel about the wheel hub for transporting the frame structure across the ground;
the ground wheels of at least the front frame portion being steerable relative to the front frame portion;
the front and rear frame portions being mounted for pivotal movement each relative to the other about an axis longitudinal of the direction of travel;
and four suspension assemblies each arranged to mount one of the ground wheels on a respective end of a respective one of the axles and each arranged to allow suspension movement of the axle in a suspension direction generally upwardly and downwardly relative to the respective ground wheel in response to changes in ground level.
Preferably the vehicle includes an engine and a cab mounted wholly on the front frame portion and includes a load mounted wholly on the rear frame portion.
Preferably there is provided a limit stop for limiting said pivotal movement of said frame portions.
It is a further object of the present invention to provide an improved steering system for a vehicle which uses two matching hydraulic cylinders to effect steering movements of the two steered wheels in which leakage of fluid across the pistons of the cylinders is automatically compensated.
According to a second aspect of the invention there is provided an agricultural vehicle for moving over agricultural terrain comprising:
a vehicle frame structure for supporting elements to be transported;
a pair of ground wheels each having a wheel hub mounted on a respective side of the frame structure for rotation of the ground wheel about the wheel hub for transporting the frame structure across the ground in a direction of travel;
each wheel hub being carried on a respective one of two first mounting members for pivotal steering movement relative thereto about a substantially vertical steering axis;
each first mounting member including a respective one of two double acting hydraulic cylinders each extending between a mounting point on the mounting member and a mounting point on the hub such that extension and retraction of a piston in the cylinder between two end positions of the piston causes movement of the wheel hub between two extreme steering positions thereof;
and a control system for supplying hydraulic fluid to the cylinders for effecting synchronised steering movement of the wheel hubs to effect steering of the vehicle, the control system including:
a source of hydraulic fluid;
a valve operable to selectively direct fluid from the source into a left turn duct and a right turn duct, the valve being operable in response to manual input of a required turning direction;
the left turn duct being connected to one end of one of the cylinders such that supply of fluid thereto at a required steering pressure causes actuation of the cylinder to effect turning of the respective wheel in a direction to effect steering to the left;
the right turn duct being connected to one end of the other of the cylinders such that supply of fluid thereto at a required steering pressure causes actuation of the cylinder to effect turning of the respective wheel in a direction to effect steering to the right;
an interconnection duct connecting fluid between the other end of said one cylinder and the other end of said other cylinder such that actuation of said one cylinder to effect turning of the respective wheel in a direction to effect steering to the left causes communication of fluid to the other cylinder to effect turning of the respective wheel in a direction to effect steering to the left and such that actuation of said other cylinder to effect turning of the respective wheel in a direction to effect steering to the right causes communication of fluid to said one cylinder to effect turning of the respective wheel in a direction to effect steering to the right;
a first compensation duct including a first pressure relief valve arranged between the interconnection duct and a high pressure point;
a second compensation duct including a second pressure relief valve arranged between the interconnection duct and a low pressure point;
each of the first and second pressure relief valves being arranged to prevent flow of fluid in one direction and to allow flow of fluid in the opposed direction when a pressure difference there across exceeds a predetermined pressure greater than the required steering pressure and less than a maximum operating pressure of the source;
such that, when one cylinder reaches one of its end positions before the other cylinder reaches its respective end position, fluid is caused to flow between the interconnection duct and one of the high pressure point and the low pressure thereby automatically re-aligning the wheels to accommodate any leakage of fluid across the pistons.